Busy Indicator with converter to show a message

indicator.xaml

<?xml version="1.0" encoding="utf-8" ?>
<ResourceDictionary
    x:Class="MyApp.Styles.Indicator"
    xmlns="http://xamarin.com/schemas/2014/forms"
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml">

    <ControlTemplate x:Key="MainTemplate">
        <Grid BindingContext="{TemplateBinding BindingContext}">
            <ContentPresenter Grid.Row="0" />

            <!--  'Busy' indicator  -->
            <StackLayout
                Grid.Row="0"
                BackgroundColor="{DynamicResource BackgroundIndicatorColor}"
                HorizontalOptions="FillAndExpand"
                IsVisible="{TemplateBinding BindingContext.IsBusy}"
                VerticalOptions="FillAndExpand">
                <StackLayout
                    HorizontalOptions="CenterAndExpand"
                    VerticalOptions="CenterAndExpand">
                    <Frame
                        Margin="10"
                        Padding="10"
                        CornerRadius="40"
                        HeightRequest="100"
                        WidthRequest="200">
                        <StackLayout>
                            <ActivityIndicator
                                BackgroundColor="Transparent"
                                HeightRequest="48"
                                HorizontalOptions="Center"
                                IsRunning="{TemplateBinding BindingContext.IsBusy}"
                                IsVisible="{TemplateBinding BindingContext.IsBusy}"
                                VerticalOptions="Center"
                                WidthRequest="48"
                                Color="{DynamicResource IndicatorColor}" />
                            <Label 
                                IsVisible="{TemplateBinding BindingContext.IsBusyText,
                                                Converter={StaticResource StringHasValueConverter}}"
                                HorizontalOptions="Center"
                                HorizontalTextAlignment="Center"
                                Style="{DynamicResource TextPrimaryColor}"
                                Text="{TemplateBinding BindingContext.IsBusyText}" />
                        </StackLayout>
                    </Frame>
                </StackLayout>
            </StackLayout>
        </Grid>
    </ControlTemplate>
</ResourceDictionary>